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The upper layer of the world’s oceans has warmed significantly since 1993, a strong indicator of how the planet is heating up, according to a new study of the heat contained in the seas. After analyzing numerous estimates of heat in the upper ocean — from the surface to a depth of about 2,000 feet — the researchers found that the seas absorbed about 0.6 watts of energy per square meter from 1993 to 2008 — enough stored energy to power 500 100-watt light bulbs for each of the planet’s 6.7 billion people. Recent temperature data was collected with 3,200 robot floats spread around the world’s oceans, while earlier data was recorded with bathythermographcs, or XBT probes, which were dropped from ships to measure water temperature. “We’re seeing the global ocean store more heat than it gives off,” said John Lyman, an oceanographer at the National Oceanic and Atmospheric Administration’s Joint Institute for Marine and Atmospheric Research and lead author of the study, published in the journal Nature. In fact, as the largest sink for solar heat in the Earth’s climate system, the researchers estimate that about 80 to 90 percent of the increased heat ends up in the oceans. Since seawater expands as it is heated, the researchers say the warming ocean temperatures likely account for about one-third to one-half of global sea rise.

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The Warriors of Qiugang, a Yale Environment 360 video, chronicles a Chinese village’s fight against a polluting chemical plant. It was nominated for a 2011 Academy Award for Best Documentary Short.
Watch the video.